Using Possession on these machines is akin to "hacking" them in previous BioShock games, and will instantly net you a pile of between 1 and 40 Silver Eagles on the ground in front of the machine. It's not necessarily recommended to use possession on Vending Machines in 1999 mode as it only gives a small amount of money and requires a large amount of Salts to use, although with the excessive amount of supplies to be found lying around it might not be a bad idea.

Also, if playing on 1999 mode and trying to obtain the Scavenger Hunt achievement/trophy do not purchase anything from the Dollar Bill machines.